I. Field
The present disclosure relates generally to electronics, and more specifically to an output circuit for power amplifiers and other circuits.
II. Background
A power amplifier is an amplifier that can provide high output power for a signal to be transmitted. Power amplifiers are used in virtually all wireless communication systems to provide amplification and output drive for signals prior to transmission over the air. For example, power amplifiers are used in Code Division Multiple Access (CDMA) systems such as CDMA 1X systems and Wideband-CDMA (W-CDMA) systems, Time Division Multiple Access (TDMA) systems such as Global System for Mobile Communications (GSM) systems, etc. Power amplifiers are used in wireless devices as well as base stations.
Power amplifiers are typically required to meet various system specifications for output power level, harmonics attenuation, etc. CDMA and GSM systems also require a wireless device to be able to transmit at a high maximum power level (e.g., +33 dBm for GSM and +27 dBm for CDMA) and to adjust its transmit power over a wide range (e.g., 30 dB or more for GSM and more than 70 dB for CDMA). Power amplifiers and supporting circuits that can provide the required performance with low power and small area are highly desirable.